Fluid pressure responsive differential bellows switch device



April 14, 1953 B. J. W|| 5ON 2,635,153

FLUID PRESSURE RESPONSIVE DIFFERENTIAL BELLOWS SWITCH DEVICE 2 SHEETS- SHEET l Filed June l2, 1950 25 l e gmc/nto@ 6 26' urziorz J. Maison a Wwf Wi @ff/27? A TTORNEY April 14, 1953 B. J. WILSON 2,635,153

FLUID PRESSURE RESPONSIVE DIFFERENTIAL BELLOWS SWITCH DEVICE Filed June 12, 1950 2 SHEETS-SHEET 2 F13 .42 h j 5 mi 55 4 n vv Il'. 'I Z .vv T. .70 i g Il w my f uw? Patented Apr. 14, 1953 FLD PRESSURE RESPONSIVE DIFFEREN- TIAL BELLOWS SWITCH DEVICE Burton Wilson, Champaign, Ill., assigner to theUnited States of America the Secretary of the Army as represented byv Application .ruse 1.2, 195o, serial No. 167,597

2' Claims.

The' invention relates to controls responsive to* liquid iiow in conduits, and especially where a minimum rate oi flow or more must be maintained to preserve systems or devicesin safe operating conditions.

TheY invention is particularly designed for' response to' flow of` coolant to devices which would be damaged if the coolantv is not supplied in adequatequantity per unit of time, so as to either remedy'the deficiency, or to stop or change op" eration*A ofj thev cooled element tol prevent damage.

An object ofthe invention is to improve the construction of such control devices which utlize the dinerence between the static pressure in a coolant supply'd'uct and resultants of static pressure and velocity head of the coolant. nowing through the duct, to respond properly and control operation of a cooled device so as to prevent damaging operation of the latter when inadequately cooled.

It isa speciiic object of the invention to present anovel construction in a switch operatively associated with a differential bellows device so as to respond effectively to diierentials of pressure in two' bellows, and which will be inexpensive to manufacture, simple in action, and maintenance, and easily adjustable to vary the response condition at which the switch is desired to operate.

The invention is particularly valuable in cooling systems for radio tubes of transmitters and radar units, and has been found especially im.- portant for use; in eld equipment of the kinds named` where liabilities of impairment of flow by' impurities inthe coolant are especially great.

I-n theseV systems water is usedi as the coolant. It is often. necessary in eldv units to remove detritus from the conduit with which the dliierential bellows is connected, and it is therefore an important aim ofv this invention to provide a construction wherein rapid access to the restricted Pitot ports and passages ci the coolant duct and bellows connection may be gained by simple procedure, yet using a construction which is rugged and eiTective for its control function. It is specifically applied to the use oi Pitot tubes, enabling quick exposure of the now-incident apertures for cleaning. without uncoupling the duct pipe.

Additional objects, advantages and features of invention will bemanifest from the disclosure of this application and reside in specific construction, combination and arrangement of parts described? and shown, or understood therefrom. The invention may" be applied to uses other- (Cl. 20G-81.9)

wise than speciflcally named for control or other purposes by responding to exceptional ilud flow conditions, as will be readily understood from the following description and accompanying drawings, wherein:

Figure 1 is a frontV elevation of a control unit embodying the invention,vpartly in section;

Figure 2 is a cross section thereof on the line 2 2 of Fie. 1.

Figure 3 is a fragmentary section on the line 3 3 of Fig. 2.

Figure 4 is a perspective view of the unit of Fig. 1.

Figure 5 is an exploded perspective view showing the heads and the duct detached.

The system herein disclosed is generally similar to that in the disclosure of the application of Steigerwalt, S. N. 531,191, iiled November 27'. 1945, for Differential Bellows Switch, now Patent No. 2,508,584 of May 23, 1950.

Referring to the drawings, there is shown a differential bellows switch device responsive to differences in static pressure and static pressure plus velocity head or velocity head components, in a conduit through which a coolant, such as water, nows to a point of heat exchange.

The device in its present embodiment comprises a base plate IU as a support, which may be located in a position convenient for access, over and upon which are mounted two generally cylindrical coaxially expandible and contractible bellows l l and larranged end to end, their outer ends being closed by means Voi stationary heads i3 and I4 respectively which extend below the bellows and rest upon the base plate l0. The

tops of these heads are planiiorm at a common level, and the heads are recessed at theirV inner sides in communication with the respective bellows and have respective vertical ports I5 and I6 extending upwardly from the recesses through the upper faces of the heads. Set in these ports there are respective Pitot tubes ll and I8 closed at their upper extremities but having apertures i9 and 2e therein near their extremities. and opening in opposite directions coincident with the axis of the duct 34 hereinafter described.

The mutually adjacent ends of the bellows are joined to a plate or iloating head 2l having' a rigid integral radial arm 22 extended therefrom substantially parallel to the plate l0. A bracket.

23 is secured to the plate lo, having a vertical' planiform switch-carrying plate 23' extending above and below the plate. A switch assembly 2c, is mounted pivotally on this plate 23 for oscillation in a vertical plane beside the plate 23',

approximately normal to the arm 22. The pivot for this switch assembly may be a switch assembly bolt 25 located near the lower end of the switch assembly and engaged through the plate 23. Engaged in a nut 25 secured to the plate 23' there is an adjustment screw 26 impinging against the lower end of the case 24' and having a locknut' 26". This limits movement of the switch case on its pivot, and serves to adjust the upper end of the switch toward the arm 22 or allow it to move from the arm. The switch proper consists of a leaf spring or blade 21, in the present instance nxed on the lower part of the case 24' of the switch assembly and extending a distance above the case and past the arm 22. The blade rests constantly against the arm 22, maintaining the latter under suicient stress to hold the lower end of the case at all times against the adjusting screw 26', which determines its position under pressure of the blade 21. A iixed contact 28 is mounted on the case exposed so as to be engaged by the spring blade 21 when the latter is pressed far enough horizontally by the arm 22.

` Terminals 29 are mounted on the case 24', one connected to the contact 2S, and the other to the base of the spring blade 21 conventionally.

, The bellows H and l2 are inherently resilient and tend to assume a medial position where theirv opposing stresses are balanced. In this state, it will be appreciated that if liquid under unbalanced pressures is admitted through the ports l and it, the predominating pressure will move the arm 22 toward the bellows having the lesser pressure.

VMounted on the heads i3 and i4 there are respective caps 3S and 3l with gaskets 32 interposed, the caps being secured by suitable screws 33 of which two are shown in each cap. Welded in and extending through these caps there is a duct 34, consisting of a simple cylindrical tube parallel to the axis of the bellows, its ends eX- tending suiliciently beyond the caps to permit conventional iniiuent and eiiluent conduit connections or couplings 35 detachable or displaceable, such as hose or pipe. In the uses to which the invention has heretofore been applied, flexible hoses 35 have been clamped on the ends of the duct, one leading from a water supply and the other to a point of discharge.

The caps and the duct tube are bored at their lower sides to receive freely and simultaneously therethrough the upstanding Pitot tubes i1 and iii, which stop short of the upper side of the duct 3Q when the caps are secured iirmly upon the heads I3 and I4. When so assembled, it will be seen that the openings i9 and 2U in the Pitot tubes are presented longitudinally of the tube and outwardly and away from the respective bellows with which the tubes communicate. In the arrangement shown, it will be seen that the device may be so adjusted that at a balanced condition of pressure in the bellows, the arm 22 may be in an engagement with the switch spring 21 holding the latter under moderate tension but without pressing it against the contact 28 by which a circuit could be closed. This also holds switch assembly case against the adjusting screw so that the position of the contact 28 Vwithrespect to the spring 21 at a predetermined pressure resultant in the position of arm 22 may represent a normal operating condition and position of the parts and the systemswith which the device may be associated as'a'control. As shown in Figures l and 3, the

4 arrangement would be suitable for use, for instance, where the right end of the tube is the iniiuent one, the liquid leaves the tube toward the left. Thus, as long as a sufficient flow of the liquid is maintained to the cooling system the predominance of pressure including both static pressure and velocity head, will hold the bellows l2 so extended against the moderate pressure in the bellows l I as to permit the switch arm 21 to swing away from the contact 28. Should the coolant supply fail however, or its velocity fall to an objectionable degree, or obstruction of the orice 22 occur, the predominance of pressureV at the right in the bellows l2 will be relieved, and the inherent resilience of the two bellows will cause corresponding movement of the arm 22 toward the right, pressing the spring 21 upon the contact 28. This mai7 be used in various ways, as will be readily understood, as, to close an alarm circuit; to close a solenoid circuit or other device circuit to open or close the circuit to the radio tube or other element then threatened, as for instance, a rectier tube or other tube in a circuit for transmission or reception of radiant energy.

1t will be appreciated that the apertures in the Pitot tubes can become blocked or partly obstructed by detritus such as threads and bers which are especially apt to get into the coolant liquid incident to field operations oi' military units, especially in combat service. In case such obstruction should occur, the arrangement of the Pitot tubes is such that an immediate indication wil be given because of the change of pressures in the bellows. It will then be possible for an attendant to remove the assembly screws 33 holding the caps 3i) and 3i in place, so that the tube 3d may be lifted from the device with the caps. With looped hose connected to the tube 32, the separation of the caps from the heads may be done without disconnecting the duct couplings. This exposes the Pitot tubes for cleaning with facility, and if the hoses are disconnected it also makes possible an optical inspection of the interior of the duct 3,4 and cleaning of the latter. In case the Pitot tubes l1 and i8 are threaded and screwed into the heads, removal and cleaning of the passagesy therethrough becomes a very simple matter.

I claim:

1. In a diiierential bellows switch control device comprising opposed bellows having `fixed stationary heads at the distal ends of the bellows and pressure-responsive movable heads at the inesial ends of the bellows, a switch device operatively connected with the movable heads for movement thereby so as to be held toward one limit by normal differentials of' opposing pressures in the bellows, and to be moved to an exceptional position by variation toward a given eXtreme in the resultant of the two pressures; the construction wherein the xed heads have ports therethrough from respective bellows, respective outstanding'parallel Pitot tube nipples set in said ports, said Pitot tube nipples extended from'the heads inthe same direction,'and cap members separably connected vwith the heads around the bases of the Pitot tube nipples and having a duct tube xed therethrough, said caps and duct tube having openings therethrough spaced and positioned to receive the Pitot tubes simultaneously and slidably therethrough, and means to secure the caps separably upon the heads in fluid-tight relation, with said Pitotr tubes extending into the duct tube,rthe openings in said Pitot tube nipples being presented in opposite directions longitudinally of the duct, whereby a differential of static and velocity head pressures will be manifest in the bellows proportionate to the rate of flow of liquid through the duct.

2. The structure of claim l wherein said switch comprises a stationary base, a case pivoted thereon for movement in a plane generally coincident With the path of movement of said switch device to and from said exceptional position, a stop xed with the base adjustable in said plane to engage a movable part of the case and limit pivotal movement thereof in one direction, said switch having a leaf spring switch blade having a free end extended a substantial distance radially from the pivot of the case and swingable in said plane, said blade having a closed switch position adjacent the case and tending inherently to move to an open position and beyond, the said switch device having an arm fixed to the movable heads of the bellows and movable therewith generally in the direction of swing of said blade and in a linear path intersecting the blade medially and transverse to said rst named plane, said arm having a medial position spaced from the closed position of the free end of said blade for translative movement by the said connected heads of the bellows under variations of differential in pressures in the bellows, said arm being positioned against said blade to engage the latter so as to apply flexing moment thereto and therethrough to the case acting toward said stop, and a contact On the case in the path of iiexure of the blade opposite the arm, whereby said blade tends to hold the switch open yieldable to said arm, and holds the rst named part of the case against said stop throughout adjustment positions of the stop.

BURTON J. WILSON.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,627,896 Hanson May 10, 1927 2,284,644 Dubilier June 2, 1942 2,508,584 Steigerwalt May 23, 1950 

